WASHINGTON — Republican congressional leaders are urging the White House to stop sharing classified information with the United Nations after learning that U.N. commanders left behind a cache of secret U.S. intelligence material when they pulled out of Somalia earlier this month.

The Capitol Hill lawmakers, including Senate Majority Leader Bob Dole of Kansas and House Speaker Newt Gingrich of Georgia, said the incident raises questions about the agreements between the United States and the United Nations in pursuing joint peacekeeping missions.

They have also taken the unusual step of asking President Clinton for the immediate suspension of intelligence-sharing with U.N. peacekeeping operations unless the life or safety of deployed military forces is in jeopardy.

"This incident calls into question the adequacy of existing U.S. procedures and policies on sharing intelligence information with elements of the United Nations engaged in peacekeeping operations," the 11 lawmakers said in a letter to the White House this week.

They added that the situation "stands in direct contradiction" to the assurances Congress was given by Administration officials that U.S. intelligence materials would not be compromised.

The documents were found by the U.S. military in the U.N. headquarters compound in Mogadishu, the Somali capital, after it had been abandoned at the end of the peacekeeping mission earlier this month. U.S. troops had been sent back to Somalia to provide cover for the departing peacekeepers.

Administration officials have declined to identify the documents other than as "classified papers and some floppy disks."

They said the matter is under internal investigation by the military's Central Command in Florida, which ran the Somali evacuation operation, and the Joint Chiefs of Staff office in the Pentagon. They also said officials are looking at ways to apply new safeguards to prevent problems.

"This is an issue of concern to us, and it is being actively pursued," Navy Lt. Cmdr. Scott Campbell said. "We are keeping the congressional committees apprised of the situation as we go along with this. We're also coordinating with United Nations officials to try to assure that adequate procedures are in place to properly handle U.S.-supplied information."

He said that some of the material has been destroyed but that other documents were brought back to the United States for further review. He said none of the materials are believed to have reached the hands of Somali warlords in Mogadishu.

But he contradicted Administration sources who have contended that the material was not all that sensitive in the first place.

"I wouldn't say it was low-grade stuff," he said. "Some of the classifications made the U.S. personnel wonder why the U.N. people even had this."

Madeleine Albright, the U.S. ambassador to the United Nations, told a House Appropriations Committee hearing this week that "we are taking this matter very, very seriously."

"When we have all the facts, we will take the appropriate action," she said.

She described the material as "potentially sensitive U.S. government-origin materials that were left in some unlocked boxes."

"But there is no evidence at all that the information was compromised," she said.

She also told the House committee that the United States has often shared secret intelligence data with U.N. peacekeepers because it makes the joint operations "more professional."

She said the United States provides the information because it can save the lives of peacekeepers, help the enforcement of U.N.-imposed sanctions and provide critical data about refugee flows between neighboring nations in conflict.

"A certain amount of intelligence is very important for that," she said.

"But let me assure you," she told the House members, "that at any stage where the risk outweighs the benefits, we will not do it. And so we are investigating this very carefully."

Others signing the congressional letter were Sen. Jesse Helms of North Carolina, chairman of the Senate Foreign Relations Committee, and Rep. Larry Combest of Texas, chairman of the House Select Committee on Intelligence.